how to continuously rotate an image in the video editor
You add a transform effect strip then keyframe the start and end with rotation changes. Otherwise you can add a couple small rotation keyframes to check speed then add a Cycle modifier to the f-curve of the .blend that extends the animation out past the keyframes. 
f-curve modifiers 2.6 wiki


  Cycles mode - Repeat with Offset
  : Repeats the curve data, but offsets the value of the first point to the value of the last point each cycle.